1. Field of the Invention
Aspects of the present invention relate to wireless communications using multiple-antenna systems, and more particularly, to a wireless communication system in which space-division multiple access (SDMA) communication which can generate a transmission signal more effectively even when reducing feedback data.
2. Description of the Related Art
Currently, studies for providing various multimedia services, such as, voice service in a radio communication environment and also supporting data transmission in high quality and high speed have been actively conducted. From these studies, space-division multiple access (SDMA) communication technologies using Multi-antenna have been actively developed.
The SDMA denotes a technology that allows a station to transmit (or receive) signal (i.e., at least one data stream) to (or from) multiple users in a same bandwidth and time simultaneously, via a plurality of antennas. The SDMA technology increases the data rate and total capacity of wireless communication systems by using radio resources (i.e., frequency bandwidths, time, etc.) more effectively.
Signals transmitted, via a plurality of antennas using SDMA technology, are subjected to beam-forming, via a preceding scheme, according to channel state information at a transmitter (i.e., base station “BS”). In general, in a closed-loop SDMA system, user terminals provide feedback information associated with the channel state information to a base station (BS), and the base station (BS) selects the user terminal using the feedback information and performs beam-forming in which multiple streams of the signals are emitted from transmit antennas in accordance with a precoding scheme, i.e., with independent and appropriate phase (and gain) weighting such that the signal power is maximized at the receiver input and a multipath fading effect is minimized.
In order to improve the performance of the beam-forming, an amount of the feedback information has to be increased. However, since each of the user terminals is required to transmit each of the feedback information back to the base station (BS), radio resources can be exceedingly consuming. As a result, any unreasonable increase in the amount of feedback can be very disadvantageous.
In addition, the feedback information is transmitted to the base station (BS), via a feedback link formed between the user terminal and the base station (BS); however, such a feedback link can be adversely affected by fading and noise. Accordingly, errors may occur in the feedback information while the feedback information is being transmitted back to the base station (BS). As a result, multiple problems can be created at the base station (BS) to perform the beam-forming.
Therefore, there is a need for a system and method of SDMA communication that may enable a base station to effectively perform beam-forming without unreasonably increasing the amount of the feedback information.